1. Technical Field
The present invention relates to a wiring board, a method of manufacturing the same, an element housing package, an electronic device, an electronic apparatus, and a moving object.
2. Related Art
Ceramic wiring boards are more excellent than organic wiring boards from the viewpoint of thermal conductivity, heat resistance, chemical stability, and the like. Thus, ceramic wiring boards can increase the density of wiring boards and contribute to a reduction in the size of electronic apparatuses.
Such a ceramic wiring board is provided with a through wiring passing therethrough in a thickness direction, and thus can be used as an interposer substrate.
For example, JP-A-2008-004927 discloses a laminated mounting structure that includes a first substrate, a second substrate, and an intermediate substrate which is provided between the first and second substrates. The intermediate substrate is provided with a through hole that passes therethrough in a thickness direction. Further, an elastic conductive ball having a size larger than a depth and an inner diameter of the through hole is pressed into the through hole. Thus, an electrode provided in the first substrate and an electrode provided in the second substrate are electrically connected to each other through the elastic conductive ball.
On the other hand, ceramic wiring boards have been used as substrates for packages of various types of devices, on the basis of excellent gas impermeability derived from the ceramics.
A piezoelectric device using a piezoelectric material such as, for example, quartz crystal has been used in many fields as a vibration device such as a piezoelectric vibrator, a resonator, and a filter. Among these, the piezoelectric vibrator (vibration device) is frequently used in electronic apparatuses as a time source, a timing source such as a control signal, a reference signal source, and the like. The piezoelectric vibrator includes a piezoelectric vibrator element and an excitation electrode which is provided on both principal surfaces of a vibration region in the piezoelectric vibrator element. In order to use the piezoelectric vibrator as the above-described time source and the like, the piezoelectric vibrator is required to be accurately oscillated at an intended resonance frequency.
However, in the piezoelectric vibrator element, frequency characteristics may change unintentionally due to the aging deterioration of the material thereof or the attachment of impurities. Consequently, the piezoelectric vibrator element is accommodated in a package, and the package is airtightly sealed, thereby suppressing the material deterioration and the attachment of impurities on the piezoelectric vibrator element over a long period and suppressing changes in frequency characteristics. On the other hand, electric wiring that connects the inside and outside of the package is required in order to drive the piezoelectric vibrator element, and thus through wiring is formed in the package.
A ceramic wiring board is used as a substrate constituting a portion of such a package for the piezoelectric vibrator.
Consequently, when the ceramic wiring board disclosed in JP-A-2008-004927 is applied to a ceramic wiring board for a piezoelectric vibrator, it is possible to form a through wiring passing through the ceramic wiring board by using an elastic conductive ball.
However, since the elastic conductive ball is merely pressed into the through hole, it is difficult to airtightly seal the through hole.